1. Field of the Invention
The invention relates to computer numerically controlled machines and in particular to automated machine component evaluation for use in aligning and maintaining such machines.
2. Description of Related Art
Computer numerically controlled (CNC) machines are used to accurately machine and produce parts in an efficient and repeatable manner. CNC machines typically use compensation techniques to account for linear positional errors, and tool length errors. Methods and apparatuses are conventionally available to manually evaluate a CNC machine's geometric conditions with respect to their various degrees of freedom of motion to determine whether alignment or machine restoration is required. Automatic tool length compensation is also available to evaluate machine rotary tool lengths and compensation lengths for use by CNC machines. These techniques are used for insuring machining accuracy.
Various devices, probes, and systems have been developed for accurately and automatically measuring tool length errors and work piece dimensions. Examples of such systems, using sensor apparatuses commonly referred to as touch trigger probes, are illustrated in U.S. Pat. No. 4,382,215 entitled "System and Method of Precision Machining", by Allan R. Barlow and William A. Hunter, which issued on May 3, 1983; U.S. Pat. No. 4,428,055, entitled "Tool Touch Probe System and Method of Precision Machining", by John R. Zubrick and John R. Kelley, which issued on Jan. 24, 1984; and U.S. Pat. No. 4,899,094 entitled "Method of Calibration for an Automatic Machine Tool" by David I. Pilborough, which issued on Feb. 6, 1990, and is assigned to Renishaw plc in England. These patents provide background information as well as illustrate some of the prior art.
Good machine maintenance involving machine evaluation and restoration is important for accurate and precision machining. Conventional machine maintenance evaluation is labor intensive and dependant. Because of the amount of human intervention required differences occur in the machine's evaluation and restoration. Different technicians may perform the maintenance procedures slightly differently. Environmental differences such as temperature may also effect the alignment of machine components.
Another problem associated with conventional restoration procedures relates to repeatability which is a particular concern for machining operations using statistical analysis to improve quality.
Therefore, there exists a need to accurately evaluate a machine's geometric condition during the machining process without significantly interrupting the flow of work through the machine. There is also a need to evaluate and restore the machine in a quicker more repeatable manner than is conventionally available.